In Campbell v. Graham-Armstrong (1973) 9 Cal.3d 482, plaintiffs had accepted part-time employment to teach a one-session kindergarten class requiring 180 minutes of instruction per day. Their salary was substantially below the salary of full-time employees who taught a two-session class, each consisting of 150 minutes. At the time in question, section 11003, since repealed, provided: "The minimum schoolday for pupils of kindergartens . . . inclusive of recesses . . . ." Its closest contemporary counterpart is section 46117, which reads: "The minimum schoolday for pupils in kindergartens is 180 minutes inclusive of recesses, and no units of average daily attendance shall be credited for attendance in kindergarten classes if the minimum schoolday of such classes is less than 180 minutes." In Campbell, the Supreme Court pointed out that section 45024 defined a full-time certificated employee as one working not less than the minimum schoolday. It further pointed out that section 45053 described "full-time" as meaning not less than the minimum schoolday for each day the schools of the District are maintained. Reading these sections in conjunction with section 11003, the court held that plaintiff teachers had established their status as full-time employees by showing that they had taught for the minimum schoolday as prescribed by the Education Code, and in view of section 44924 could not waive their rights to the benefits of the statute.